Assessment of lesion transmurality

Abstract

A method and apparatus for treating a body tissue in situ (e.g., an atrial tissue of a heart to treat) atrial fibrillation include a lesion formation tool is positioned against the heart surface. The lesion formation tool includes a guide member having a tissue-opposing surface for placement against a heart surface. An ablation member is coupled to the guide member to move in a longitudinal path relative to the guide member. The ablation member has an ablation element for directing ablation energy in an emitting direction away from the tissue-opposing surface. The guide member may be flexible to adjust a shape of the guide member for the longitudinal path to approximate the desired ablation path while maintaining the tissue-opposing surface against the heart surface. In one embodiment, the ablation member includes at least one radiation-emitting member disposed to travel in the longitudinal pathway. Transmurality can be assessed to approximate a location of non-transmurality in a formed lesion.

Description

CROSS-REFERENCE TO RELATED APPLICATION[0001]This patent application is continuation-in-part of commonly assigned U.S. patent application Ser. No. 11 / 102,091 filed in the names of co-inventors Gregory G. Brucker, Adam L. Berman, Damian A. Jelich, Dana R. Mester and Robert W. Clapp on Apr. 8, 2005 and entitled “Apparatus and Method for Guided Ablation Treatment” and filed as a continuation-in-part application of U.S. patent application Ser. No. 10 / 975,674 filed Oct. 28, 2004 titled “Apparatus and Method for Laser Treatment” and which claims priority to U.S. Provisional Patent Application Ser. No. 60 / 516,242 with an assigned filing date of Oct. 31, 2003. The present application claims priority to all of the foregoing.BACKGROUND OF THE INVENTION[0002]1. Field of the Invention[0003]The present invention relates to surgical instruments for laser cardiac ablation procedures. More particularly, the invention relates to an ablation apparatus with a guide member to guide the ablation apparatu...

AI Technical Summary

Benefits of technology

[0030]According to a preferred embodiment of the present invention, a method and apparatus are disclosed for treating a body tissue in situ (e.g., atrial tissue of a heart to treat) atrial fibrillation. The method and apparatus include identifying a patient with atrial fibrillation and accessing a surface of the tissue. A lesion formation tool is positioned against the accessed surface. The lesion formation tool includes a guide member having a tissue-opposing surface for placement against a heart surface. An ablation member is coupled to the guide member to move in a longitudinal path relative to the guide member. The ablation member has an ablation element for directing ablation energy in an emitting direction away from the tissue-opposing surface. In a preferred embodiment, the guide member is flexible to adjust a shape of the guide member for the longitudinal path to approximate the desired ablation path while maintaining the tissue-opposing surface against the heart surface. In one embodiment, the ablation member includes at least one radiation-emitting member disposed to travel in the longitudinal pathway. In another embodiment, the guide member has a plurality of longitudinally spaced apart tissue attachment locations with at least two being separately activated at the selection of an operator to be attached and unattached to an opposing tissue surface. Various means are described for the attachment including vacuum and mechanical attachment. The guide member may have a steering mechanism to remotely manipulate the shape of the guide member. In another embodiment, the ablation member is attached to a reciprocator to move the radiation-emitting member back and forth within the longitudinal pathway over a fixed distance in an oscillating manner to distribute the radiation uniformly in a line. In another embodiment, the reciprocator contains a mechanism for changing the position of the radiation-emitting member in the longitudinal pathway to distribute the radiation over a longer line. In additional embodiments, the invention may include fluid flushing to the ablation member, apparatus to enhance visualization of the ablation procedure and apparatus to monitor and test for transmurality of a created lesion. Transmurality can be assessed to approximate a location of non-transmurality in a formed lesion.

Problems solved by technology

Atrial fibrillation prevents the heart from pumping blood efficiently causing reduced physical activity, stroke, congestive heart failure, cardiomyopathy and death.

Once these lines scar and heal, they disrupt electrical pathways that may cause atrial fibrillation.

This is particularly difficult when radio frequency (RF) energy is employed because it relies exclusively on thermal diffusion to create transmural lesions i.e, flow of heat from higher to lower temperature.

The cooling effect of blood on the endocardial surface within the atrium limits attainment of the temperature required to form thermal lesions.

Higher temperatures cause boiling of interstitial water creating explosions and subsequent tissue perforations.

Perforations of the atrial wall leads to a weakening of the heart structure as well as significant bleeding during surgery that must be controlled.

Additionally, high electrode / tissue temperatures can create burns and adhesion between the probe and the heart tissue.

Such adhesions can insulate the probe from the heart tissue blocking the efficient application of energy.

These procedures are also a problem for the surgeon and staff who often must stop to clean the tip of the probe.

This approach requires access into the left atrium which adds complexity and increases risk to the patient.

However in this application, the blood warms the tissue at the endocardial surface which again limits the attainment of temperatures required to cause cellular death and create transmural lesions.

As a result, laser ablation is fast and results in narrow lesions.

However, in the prior art, laser ablation for treating atrial fibrillation has been troublesome.

Viola et al. discuss problems associated with the use of laser energy to treat atrial fibrillation.

These concerns are directed to safety and reliability and note that lasers are prone to overheating because of the absence of a self-limiting mechanism.

The authors note that over-heating with lasers can lead to crater formation and eventually to perforation, especially when using pin-tip devices.

The authors note that the high power of laser ablation (described as 30 to 80 Watts) results in the laser technique not being widely clinically applied.

The mechanical effects resulting from direct heating of the myocardial tissue with laser energy results in cellular explosions caused by shock waves.

A coring of the myocardium by a laser could result in a full wall thickness perforation and resulting leakage of blood.

This reduces the longitudinal movement required to produce linear lesions but, by decreasing the coherency of the laser beam before entering cardiac tissue, and negates many of the advantages of light to more deeply penetrate cardiac tissue.

Reducing energy penetration depths increases the risk (particularly on a beating heart) of creating a lesion that is less than transmural.

A further difficulty with creating linear nonconductive lesions is the inability to verify that a truly nonconductive lesion has been produced.

If a transmural lesion is not properly formed in accordance with the Maze procedure, the treatment for atrial fibrillation may not be successful.

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